/*
 * Copyright (C) 2011 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef SKY_ENGINE_WTF_DOUBLYLINKEDLIST_H_
#define SKY_ENGINE_WTF_DOUBLYLINKEDLIST_H_

namespace WTF {

// This class allows nodes to share code without dictating data member layout.
template <typename T>
class DoublyLinkedListNode {
 public:
  DoublyLinkedListNode();

  void setPrev(T*);
  void setNext(T*);

  T* prev() const;
  T* next() const;
};

template <typename T>
inline DoublyLinkedListNode<T>::DoublyLinkedListNode() {
  setPrev(0);
  setNext(0);
}

template <typename T>
inline void DoublyLinkedListNode<T>::setPrev(T* prev) {
  static_cast<T*>(this)->m_prev = prev;
}

template <typename T>
inline void DoublyLinkedListNode<T>::setNext(T* next) {
  static_cast<T*>(this)->m_next = next;
}

template <typename T>
inline T* DoublyLinkedListNode<T>::prev() const {
  return static_cast<const T*>(this)->m_prev;
}

template <typename T>
inline T* DoublyLinkedListNode<T>::next() const {
  return static_cast<const T*>(this)->m_next;
}

template <typename T>
class DoublyLinkedList {
 public:
  DoublyLinkedList();

  bool isEmpty() const;
  size_t size() const;  // This is O(n).
  void clear();

  T* head() const;
  T* removeHead();

  T* tail() const;

  void push(T*);
  void append(T*);
  void remove(T*);

 private:
  T* m_head;
  T* m_tail;
};

template <typename T>
inline DoublyLinkedList<T>::DoublyLinkedList() : m_head(0), m_tail(0) {}

template <typename T>
inline bool DoublyLinkedList<T>::isEmpty() const {
  return !m_head;
}

template <typename T>
inline size_t DoublyLinkedList<T>::size() const {
  size_t size = 0;
  for (T* node = m_head; node; node = node->next())
    ++size;
  return size;
}

template <typename T>
inline void DoublyLinkedList<T>::clear() {
  m_head = 0;
  m_tail = 0;
}

template <typename T>
inline T* DoublyLinkedList<T>::head() const {
  return m_head;
}

template <typename T>
inline T* DoublyLinkedList<T>::tail() const {
  return m_tail;
}

template <typename T>
inline void DoublyLinkedList<T>::push(T* node) {
  if (!m_head) {
    ASSERT(!m_tail);
    m_head = node;
    m_tail = node;
    node->setPrev(0);
    node->setNext(0);
    return;
  }

  ASSERT(m_tail);
  m_head->setPrev(node);
  node->setNext(m_head);
  node->setPrev(0);
  m_head = node;
}

template <typename T>
inline void DoublyLinkedList<T>::append(T* node) {
  if (!m_tail) {
    ASSERT(!m_head);
    m_head = node;
    m_tail = node;
    node->setPrev(0);
    node->setNext(0);
    return;
  }

  ASSERT(m_head);
  m_tail->setNext(node);
  node->setPrev(m_tail);
  node->setNext(0);
  m_tail = node;
}

template <typename T>
inline void DoublyLinkedList<T>::remove(T* node) {
  if (node->prev()) {
    ASSERT(node != m_head);
    node->prev()->setNext(node->next());
  } else {
    ASSERT(node == m_head);
    m_head = node->next();
  }

  if (node->next()) {
    ASSERT(node != m_tail);
    node->next()->setPrev(node->prev());
  } else {
    ASSERT(node == m_tail);
    m_tail = node->prev();
  }
}

template <typename T>
inline T* DoublyLinkedList<T>::removeHead() {
  T* node = head();
  if (node)
    remove(node);
  return node;
}

}  // namespace WTF

using WTF::DoublyLinkedList;
using WTF::DoublyLinkedListNode;

#endif  // SKY_ENGINE_WTF_DOUBLYLINKEDLIST_H_
